In marking systems such as Xerography or other electrostatographic processes, a uniform electrostatic charge is placed upon a photoreceptor surface. The charged surface is then exposed to a light image of an original to selectively dissipate the charge to form a latent electrostatic image of the original. The latent image is developed by depositing finely divided and charged particles of toner upon the photoreceptor surface. The charged toner being electrostatically attached to the latent electrostatic image areas creates a visible replica of the original. The developed image is then usually transferred from the photoreceptor surface to a final support material, such as paper, and the toner image is fixed thereto to form a permanent record corresponding to the original.
In some Xerographic copiers or printers, a photoreceptor surface is generally arranged to move in an endless path through the various processing stations of the xerographic process. Since the photoreceptor surface is reusable, the toner image is then transferred to a final support material, such as paper, and the surface of the photoreceptor is prepared to be used once again for the reproduction of a copy of an original. In this endless path, several Xerographic related stations are traversed by the photoconductive belt.
Generally, in one embodiment, after the transfer station, a photoconductor cleaning station is next and it comprises a first cleaning brush, a second cleaning brush and after the brushes are positioned, a spots or cleaning blade which is used to remove residual debris from the belt such as toner additive and other filming. This film is generally caused by the toner being impacted onto the belt by the cleaning brushes. When the lubrication of this blade is below a necessary level, it will abrade the belt. Toner is the primary lubricant for the blade; however, a problem is with good cleaning efficiency by the cleaning brushes, the amount of toner reaching the blade can often be well below this necessary level. Without proper lubrication, this spots blade will seriously abrade the belt.
Since most toners used today are negatively charged, the embodiments throughout this disclosure and claims will be described relating to the use of a negative toner; however, when a positive toner is used, the proper opposite adjustments can easily be made.
The first brush above mentioned in prior art systems is responsible for nearly all of the filming on the photoconductive (PC) belt. This brush is positively charged to attract a negative charged toner and remove most of it from the PC belt. Adjacent to the first brush is a vacuum which vacuums the toner from the brush for later disposal. Any toner that may have acquired a positive charge will pass by the first positively charged brush and will be picked up by the second brush which is negatively charged. The vacuum is also adjacent to the second brush and should vacuum off the brush any residual positively charged toner. Then, as above noted, the spots or cleaning blade scrapes off the belt any remaining toner debris or film layer. Again, after the action of the two prior cleaning brushes there is generally not sufficient toner lubrication for an effective action by this spots blade. The cleaning blade will remove the film layer comprised of toner additives that is caused by the impact of the first brush against the toner and PC belt. The serious problem that has been encountered in this type of prior art arrangement is, as noted, that the cleaning blade does not get enough toner provided lubrication and can easily scratch and damage the belt, causing a relatively high replacement rate for both the belt and the cleaning blade. In addition, copy quality begins to deteriorate as the cleaning blade is abraded and damaged or as the film is less effectively removed from the PC belt by this blade.
Many of the low volume electrophotographic printers and some high speed marking apparatus use elastic doctor blades to remove residual toner from drum or belt photoreceptors. Improvements in the reliability of such blades are desired to minimize/reduce wear induced defects and to extend the overall life of the cleaning blade. Unloaded polyurethane and other elastomeric materials are typically useful in cleaning blade materials. Improved materials are required to extend the useful life of such blades.